Sulfonated poly(arylene-co-imide)s as water stable proton exchange membrane materials for fuel cells

A novel sulfonated poly(arylene-co-imide)s were synthesized by Ni(0) catalytic copolymerization of sodium 3-(2,5-dichlorobenzoyl)benzenesulfonate and naphthalimide dichloride monomer. The synthesized copolymers with the - SO3H group on the side-chain of polymers possessed high molecular weights revealed by their high viscosity and the formation of tough and flexible membranes. Because of the introduction of electron donating phenoxy groups into naphthalimide moieties, the hydrolysis of the imide rings was depressed. The resulting copolymers exhibited excellent water stability. The copolymer membranes display no apparently change in appearance, flexibility, and toughness after a soaking treatment in pressurized water at 140 degrees C for 250 h. TEM analysis revealed that these side-chain type membranes have a microphase separated structure composed of hydrophilic side-chain domains and hydrophobic polyimide main chain domains. The proton conductivities of copolymer membranes increased with the increase of IEC and temperature, reaching values above 3.2 x 10(-1) S/cm at 80 degrees C, which are higher than Nafion 117 on the same measurement conditions. The methanol permeability of the copolymer membranes was one order lower than that of Nafion 117. Consequently, these Materials proved to be promising as Proton exchange membranes. (c) 2008 Elsevier B.V. All rights reserved.